Modeling the mucinous glycocalyx to unravel receptor pattern recognition by influenza A viruses

Abstract

Influenza A viruses (IAVs) exploit host glycans in airway epithelial mucosa for entry and infection. Rapid detection of changes in IAV glycan‐binding phenotype can provide early indication of virus transmissibility and infection potential. IAVs use hemagglutinins (HAs) to bind sialic acids, and a switch in HA specificity is considered a prerequisite for transmission from birds to humans. Likewise, understanding the molecular mechanisms used by the viruses to overcome the mucin barrier may guide the development of more effective antiviral therapies. This presentation will describe the development of a glycan array platform, which uses synthetic mimetics of mucin glycoproteins to model how receptor presentation in the mucinous glycocalyx (i.e., glycan type, valency of the glycoconjugates, and their surface density) may impact IAV recognition. This platform utilizes machine learning to identify preferred receptor displays in the mucinous glycocalyx for adhesion of H1N1 and H3N2 viruses. Intriguingly, the arrays revealed a change in receptor pattern recognition by H1N1 upon transition from avian to mammalian cell culture. Without altering its HA affinity, the mammalian cell‐produced virus showed reduced sensitivity to surface crowding of the mucin mimetics. Using our mucin mimetics, we have also evaluated the physical protective functions of the glycocalyx on viral adhesion to cells. We found that bulky mucin mimetics lacking sialoglycan receptors inhibited the rate of H1N1 adhesion in a size‐ and density‐dependent manner, consistent with current view of the mucins as providing a protective shield against pathogens. Counterintuitively, increasing density of the mucin mimetics enhanced the retention of bound viruses. Careful characterization of SNA behavior at the RBC surface using a range of biophysical and imaging techniques revealed lectin‐induced crowding and reorganization of the glycocalyx with concomitant enhancement in lectin clustering, presumably through the formation of a more extensive glycan receptor patch at the cell membrane. Our findings indicate that glycan‐targeting pathogens may exploit the biophysical and biomechanical properties of mucins to overcome the mucosal glycocalyx barrier.